This invention relates to planar coil configurations and more particularly to such configurations employed as motion sensors, switches and other devices.
The concept of utilizing planar coil configurations to provide transducer operation as to convert, for example, motion to an electrical output signal has been described in my copending application entitled PLANAR COIL APPARATUS FOR PROVIDING MOTION SENSORS, SWITCHES AND VARIOUS STRUCTURES filed on Dec. 9, 1980 as Ser. No. 214,606.
In this application, two planar coil members are positioned one above the other in a parallel plane leaving a space between and a ferromagnetic coupling member is movably positioned in the space to thereby allow a magnetic field induced in one coil to couple to the other coil when said ferromagnetic member is moved out of said space and to prevent coupling of the field when the member is disposed within the space. This transducer has extreme advantages over the prior art devices such as conventional motion sensing structures.
Such prior art devices may employ variable resistance elements as in displacement transducers. These devices have a sliding contact or wiper arm which moves across a resistance element. The wiper is mechanically linked to a sense shaft and hence, the transducers operate on a contacting principle. It is this feature that causes them to wear out or fail under a large number of cycles.
Many other types of transducers also exist such as inductive or capacitive transducers which convert a displacement into a change of inductance or capacitance. These prior art devices are either more costly to manufacture or less reliable than the non-contacting devices using planar coils.
A switch is basically a simple form of a sensor and operates to provide a change in state in response to physical motion. In this manner, a switch is a very simple type of motion sensor. As described in the copending application and as further evident from the prior art, it is extremely desirable to provide a non-contacting motion sensor which is economical, exhibits a long lifetime and hence, increases reliability. The sensor to be described is a motion sensor which operates on the coupling or decoupling of signals between planar coils. Planar coils are well known in the art and essentially are printed circuit spiral configurations which may be fabricated by printed circuit techniques, thin film techniques or other processes.
Planar coils have been described in the above noted copending application and are also sometimes referred to as printed circuit coils. U.S. Pat. No. 4,075,591 entitled PRINTED CIRCUIT COILS issued on Feb. 21, 1978 to D. Haas depicts a spiral type coil employed to obtain a relatively large inductance without sacrificing Q. Other patents such as U.S. Pat. No. 3,757,068 entitled KEYBOARD ACTUATING MECHANISM WITH PARTICULAR FEEL AND CONTACT MECHANISMS issued on Sept. 4, 1973 to B. Musch et al. describe a switch mechanism which can be employed in a keyboard using printed circuit coils. My copending application entitled DISPLACEMENT TRANSDUCERS EMPLOYING PRINTED COIL STRUCTURES filed on Apr. 11, 1979 as Ser. No. 028,981 discloses a displacement transducer which includes plurality of planar circuit boards, each having disposed on a surface a spiral coil structure. The boards have central apertures and are positioned in a stacked array separate from one another. A magnetic member inserted into the aligned apertures of the configuration varies the coupling between coils.
The present invention also relates to a planar coil configuration, which configuration can be used as a motion sensor, a switch, as well as other configurations. This structure differs from the structure of the first described copending application in that a first board containing a planar coil configuration is stationary and a second board also containing a planar coil configuration moves with respect to the first board to effect the coupling between the coils on the stationary board. There is no need to use magnetic members. The structure, as in the copending application, is completely noncontacting and hence, possesses an extremely long life and is capable of operating without failure for a large number of operating cycles.